Prenatal tests identify infections: Routine screening tests are done to identify any infection or problem in the mother that may affect pregnancy. These tests are usually performed during the first trimester.
Some of the routine screening tests during pregnancy.
I. Blood Tests
- Identify the blood group: Blood test helps in identifying your blood group and rh factor (that is, whether your blood group is positive or negative). This is of great significance. If the mother is rh–ve and the father is rh+ve, the foetus is likely to be rh+ve. This induces the growth of antibodies for rh factor in mother. In such cases, the first pregnancy remains preserved and delivered healthy, but with the higher chances that the second pregnancy may get aborted. This is because of the presence of antibodies for the rh factor which migrate into the foetal blood circulation, causing abortion of the foetus or hyperbilirubinemia (jaundice) in the foetus leading to further complications.
- Check prenatal anaemia: Prenatal anaemia screening measures the presence of haemoglobin, and haematocrit (percentage of RBC) in your blood. Depending on the results of these tests, the doctor may advise you for other tests like, complete blood count (CBC) test or iron and ferritin levels test. A CBC looks at the number, colour, size and shape of your red blood cells. Iron and ferritin level checks the amount of iron in your body. These test results help to identify anaemia and determine its cause and severity.
The normal range of haemoglobin in females is12-16 gm/ 100 ml of blood, normal haematocrit range is 35-45% and iron level is 30-120 µg /100 ml of blood. If any of these factors remains below normal, then it indicates anaemia. ( clickable option)
- Checking for presence of Thalasemia minor trait in either or both the parents is very important. Thalasemia is a genetic disorder of development of hemoglobin chains where by the red cell survival time is reduced. Thalasemia is checked by Hemoglobin Electrophoresis. If only one parent is Thalasemia minor, then it is not much concern. However if both you and your partner are Thalasemia minors, you stand a 25% chance of having a Thalasemia major child who would require blood for its survival later. Hence in such cases your doctor would advise you to go in for a genetic amniocentesis to check the Thalasemia status of the baby.
- Check the general health of your baby: These tests are done to identify the presence of antibodies, viruses or infections that can affect you or your baby’s health. They also help to identify anaemia or any deficiency caused by micronutrients.
- Check HIV: One specific test is done to detect HIV in your blood and your body’s immunity to tackle it.
- Check your immunity: A test is done to determine your immunity against rubella, also known as German Measles.
II. Urine Tests
A urine sample test helps to identify:
Proteinuria : Presence of protein in your urine.
Glycosuria : Presence of sugar in your urine. This helps in detecting diabetes.
UTI: Presence of any Urinary Tract Infection.
Other infections: Presence of any other infection.
Diabetes screening: This is important to determine your glucose level so that the risk of gestational diabetes can be ruled out.
Glucose tolerance test: This test identifies how quickly your blood can be cleared from glucose.
Group B-streptococcus screen: A quick and simple test to identify presence of the bacteria, Group B Strep (GBS)..
Hepatitis B virus screen: This is done to identify the presence of Hepatitis B virus.
Syphilis screening test: Helps in identifying the presence of Syphilis.
III. Ultrasound scan determines the gestational age and well being of your foetus.
Ultrasound scans are done at 8 weeks, 20 weeks and 32 weeks of gestational age. These scans help to calculate accurately your EDD (Expected Date of Delivery) by determining the gestational age of the foetus in the first scan. It also helps to rule out the risks for ectopic or molar pregnancies and intra-uterine death. In the later stage of pregnancy, it helps to ensure the well being of the foetus.
- Foetal anomaly scanning test identifies the right growth of your baby.
Foetal anomaly scanning tests are performed when there is a doubt that the baby may not be developing as expected. This happens mostly if either of the parents is a carrier of a hereditary disease, or if another test has indicated that there is a problem. This test is usually done during the second trimester.
- Doppler scanning: This is a special scan used during pregnancy. Doppler scanis a special, non-invasive scan which uses black and white or colour images to examine the blood flowing through the umbilical cord between the placenta and the baby.
- Nuchal fold or Nuchal translucency is measured by ultrasound by measuring the fluid in the nape of the foetal neck, this helps to estimate the risk of Down’s syndrome.
IV. Few special tests to ensure your baby’s health.
These are not routine tests and are done when the mother or the baby is at a potential risk of some specific abnormality. They include:
- Chorionic villus sampling (CVS): A sample of the placenta is taken with a needle inserted through the abdomen or via the cervix and tested for any chromosomal anomalies. It is done at about 11 to 14 weeks.
- Amniocentesis: It is again used to detect any chromosomal abnormality. In this, a sample of the amniotic fluid surrounding the baby is taken by syringe and cells from the baby found in the fluid are tested for chromosomal abnormalities such as Down’s syndrome. This is done at about 18 weeks.
- Nuchal fold test or Nuchal translucency test: It is an ultrasound scanning done to measure the fluid in the nape of the foetus’s neck. The measurement helps to estimate the risk of Down’s syndrome. You may also be asked for a blood test to check for past or present infection with the cytomegalo virus (CMG virus) and for toxoplasmosis.